Mechanisms of Intron Mobility

Marlene Belfort,Philip S Perlman

doi:10.1074/jbc.270.51.30237

Abstract

Mechanisms of Intron Mobility

Highlights

Group I and group II introns, which splice via RNA-catalyzed pathways, can invade DNA sequences by virtue of proteins expressed from open reading frames (ORFs)1 contained within them
Group I Intron Homing—Homing is initiated by the intronencoded endonuclease, which catalyzes a double strand break (DSB) in the intron-minus allele (Fig. 1A)
This process is thought to proceed via the DSB repair (DSBR) pathway, wherein a D-loop formed as the result of repair synthesis by the invading strand serves as a template for repair synthesis of the opposite strand (Fig. 1B)

Summary

Mechanisms of Intron Mobility*

The latter possibility is favored by the underrepresentation of crossover events among the homing products.2 One such alternative pathway is the synthesis-dependent strand annealing (SDSA) model (reviewed in Ref. 5), which has been invoked as an alternative to the DSBR pathway to explain gene conversion from ectopic sites in P-element-induced gap repair in Drosophila (Fig. 1C) [6]. The 3Ј-OH of the cleaved antisense strand is used as a primer for first-strand cDNA synthesis by RT, using the pre-mRNA precursor as template [10] This sequence of events is rather analogous to the priming of cDNA synthesis by the site-specific non-long terminal repeat retroelement R2Bm [11], consistent with the group II introns representing a type of site-specific retrotransposon. Further study is needed to determine whether that pathway occurs in wild-type crosses

Intron Transposition

Proteins That Promote Intron Mobility